The present invention relates to an improvement in the a machining method utilizing a wire electrode of performing electric discharge surface treatment or grinding with respect to a work piece.
As a technique for imparting a corrosion resistance and a wear resistance through a formation of a surface modified layer in a work piece through a submerged electric discharge, there is, for example, the electric discharge surface treatment as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-148615. This technique is an electric discharge surface treatment method for metallic material, comprising two steps in which a primary machining (piling) is executed, using a green compact electrode made by a compression molding of WC powder and Co powder or the like, and then a secondary machining (re-welding) is executed by exchanging the electrode with an electrode with a relatively low electrode exhaustion such as a copper electrode. Therefore, this conventional art can form a surface modified layer with a high hardness and a large adherence for steel.
Further, in Japanese Patent Application Laid-Open (JP-A) No. 9-192937, an electric discharge surface treatment method is disclosed in which a solid surface modified layer is formed on a surface of iron steel and sintered hard alloy or the like without a re-welding process, using a green compact electrode made by a compression molding of TiH2 powder.
In the case in which the electric discharge surface treatment technique is applied to a die, the lifetime of the die may be largely improved by the improvement in the corrosion and wear resistances.
In the case in which the electric discharge surface treatment is executed for a work piece, using a form electrode as in the conventional art, for example, as shown in FIG. 9A, when an electric discharge surface treatment is executed at an electric discharge surface treatment electrode 27 for a first work piece 26, an exhaustion part 27a is formed in the electric discharge surface treatment electrode 27, and a surface modified part 28a is formed in the first work piece 26. As shown in FIG. 9B, when an electric discharge surface treatment is executed for a second work piece 29 with a different size from the first work piece 26 at the electric discharge surface treatment electrode 27 through which the electric discharge surface treatment of the first work piece 26 is executed, exhaustion parts 27b, 27c are formed in the electric discharge surface treatment electrode 27, and a surface modified layer 30 is formed in the second work piece 29. There is a problem that a non-uniformity is generated in the thickness of the surface modified layer 30 as shown in FIG. 9B, whereby a uniform surface modified layer may not be formed.
Further, a problem exists in which there is a necessity to prepare a plurality of electric discharge surface treatment electrodes corresponding to work shapes.
In order to solve these problems, it may be thought that a surface modified material or a material to be the source of the surface modified material is employed as the wire electrode itself, and by this wire electrode an electric discharge surface treatment is executed for a work piece. However, for example, the case in which Ti, W or the like is employed as a wire electrode is not practical since the electric discharge surface treatment speed is slow. Further, that a wire electrode is formed by a green compact is not practical at all since the tensile strength of the wire electrode may not be ensured.
It is an object of this invention to obtain a machining method utilizing a wire electrode and the device thereof which is suitable for a partial surface modification, specifically for a die or the like, and in which a uniform surface modified layer of predetermined characteristics may be formed to a work piece by a practical electric discharge surface treatment speed.
It is another object of this invention to obtain a machining method utilizing a wire electrode and the device thereof in which there is no necessity to prepare a plurality of electric discharge surface treatment electrodes corresponding to machining shapes.
It is still another object of this invention to obtain a machining method utilizing a wire electrode and the device thereof in which the surface roughness of a work piece such as a die may be made small through a grinding utilizing a wire electrode provided with an electric discharge surface treatment so that a high resolution of the work piece may be obtained.
According to one aspect of this invention, in a first step, an electric discharge is generated between a wire electrode and an electric discharge surface treatment electrode made of metal powder or a mixture of metal compound power or ceramic material powder or these types of powder, and a surface modified material or a material to be the source of the surface modified material is stuck on the surface of the wire electrode by the energy of the electric discharge. In a second step, an electric discharge is generated between a work piece and the covered wire electrode on which the surface modified material or the material to be the source of the surface modified material is stuck, and a surface modified layer is formed on the surface of the work piece by the energy of the electric discharge.
According to another aspect of this invention, in a first step, an electric discharge is generated between a wire electrode and an electric discharge surface treatment electrode made of metal powder or a mixture of metal compound power or ceramic material powder or these types of powder, and a hard coating is stuck on the surface of the wire electrode by the energy of the electric discharge. In a second step, a grinding is executed for a work piece by means of the covered wire electrode to which the hard coating is stuck.
Further, wherein the first step is executed while the wire electrode and the electric discharge surface treatment electrode are relatively swung inside a vertical plane of a feed direction of the wire electrode.
According to still another aspect of this invention, a wire electrode feed unit feeds a wire electrode to a work piece. An electric discharge surface treatment electrode is composed of metal powder or a mixture of metal compound power or ceramic material powder or these types of powder. A drive unit relatively moves the wire electrode to the work piece. An electric discharge generation unit supplies machining power between the electric discharge surface treatment electrode and the wire electrode and between the wire electrode and the work piece.
According to still another aspect of this invention, a wire electrode feed unit feeds a wire electrode to a work piece. An electric discharge surface treatment electrode composed of metal powder or a mixture of metal compound power or ceramic material powder or these types of powder. A drive unit relatively moves the wire electrode to the work piece. An electric discharge generation unit supplies machining power between the electric discharge surface treatment electrode and the wire electrode.
According to still another aspect of this invention, a wire electrode feed unit feeds the wire electrode to a work piece. An electric discharge surface treatment electrode composed of metal powder or a mixture of metal compound power or ceramic material powder or these types of powder. A first drive unit relatively moves the electric discharge surface treatment electrode to the wire electrode inside a vertical plane of a feed direction of the wire electrode by the wire electrode feed unit. A second drive unit relatively moves the wire electrode to the work piece. An electric discharge generation unit supplies machining power between the electric discharge surface treatment electrode and the wire electrode and between the wire electrode and the work piece.
According to still another aspect of this invention, a wire electrode feed unit feeds a wire electrode to a work piece. An electric discharge surface treatment electrode composed of metal powder or a mixture of metal compound power or ceramic material powder or these types of powder. A first drive unit relatively moves the electric discharge surface treatment electrode to the wire electrode inside a vertical plane of a feed direction of the wire electrode by the wire electrode feed unit. A second drive unit relatively moves the wire electrode to the work piece. An electric discharge generation unit supplies machining power between the electric discharge surface treatment electrode and the wire electrode.